High-temperature ferrimagnetic order triggered metal-to-insulator transition in CaCu₃Ni₂Os₂O₁₂

Ferromagnetic order-induced insulator-to-metal transitions via the double exchange mechanism have been studied widely. In contrast, ferromagnetic or ferrimagnetic spontaneous magnetization induced metal-to-insulator transitions (MITs), especially occurring above room temperature, remain extremely limited, although such magnetoelectric materials hold great potential for low-loss multifunctional electronic and spintronic devices. Here, a novel 3d/5d hybridized quadruple perovskite oxide, CaCu₃Ni₂Os₂O₁₂, was synthesized. It undergoes long-range Cu²⁺(↑)-Ni²⁺(↑)-Os⁶⁺(↓) ferrimagnetic order with a high Curie temperature of 393 K, maintaining a saturated magnetization of 2.15 μ_B/f.u. at 300 K. Intriguingly, an MIT is found to occur concurrently at the Curie temperature. Theoretical analyses reveal that the ferrimagnetic spontaneous order significantly renormalizes the electronic band structure, which can be further modified by electronic correlation and spin-orbit coupling effects, leading to the MIT via the Lifshitz-type mechanism. This work thus provides a paradigm material to realize ferrimagnetic spontaneous magnetization induced MIT at a high critical temperature toward advanced applications.